BIOMOLECULAR ASPECTS OF SPERMATOZOAN MOTILITY 221 



Relationships between Flagella and Muscle 



The evidence presented above suggests that, although fish sperm 

 flagella contain a proportion of protein that shrinks like a feeble acto- 

 myosin with ATP, there is nothing to indicate the presence of true 

 actin or myosin. The contractile protein differs from actomyosin, 

 too, in the way in which it must be prepared, and in the added 

 property of oscillation in certain circumstances. Although in the bac- 

 terial flagella there are striking x-ray relationships with skeletal 

 muscle (Astbury et al., 1955), no such similarity has yet been found 

 in the 9 plus 2 flagella, where there is also neither morphological nor 

 biochemical evidence for any very close comparison with the myo- 

 fibril. The resemblances between the 9 plus 2 flagella and muscle 

 might best be seen in the behavior of some common macromolecular 

 arrangement, particularly in its response to ATP or equivalent elec- 

 trolytes, and it is here that the soundest basis for movement might be 

 found. 



Flagella) Motion 



The oscillatory activity of flagellar gels treated with ATP suggests 

 that the property of regular contraction and relaxation may be built 

 somehow into one system, perhaps one molecule, by the circum- 

 stances of its response to nucleotides. This effect is not unlike the 

 oscillatory behavior of the extracted myofibril induced by creatine 

 phosphate (Goodall, 1956) or by addition of phosphoenolpyruvate 

 after maximal tension (Lorand and Moos, 1956). The "automatic" 

 behavior of gels might answer Bishop's (1958b) second question: 

 "How can a co-ordinated wave-like motion occur in cells whose 

 permeability, ionic balance, and metabolic integrity have been de- 

 stroyed?"; for although the organism may have lost most of its bio- 

 chemistry and all of its supply of energy, the individual "contractile" 

 molecules may still possess their permeability, ionic balance, and 

 metabolic integrity, preserved long after other cellular processes 

 have been disorganized. We might imagine the "contractile" mole- 

 cule as a complete engine in itself, self-regulatory and tireless. In a 

 physiological situation, ATP appears to have the dual function of re- 

 laxation at low electrolyte and high pH and nucleotide concentra- 

 tion, but contraction at higher electrolyte and lower pH and nu- 

 cleotide concentration. In the flagellum and in the reconstituted gel 



